NCIt definition : Persistent and usually painful erection that lasts for at least four hours in the
absence of physical or psychological stimulation, which can be caused by hematologic
disorders, including sickle cell disease and leukemia, spinal cord injuries, and medications.;
Alternative definition : NICHD: Persistent and usually painful erection that lasts for at least four hours,
in the absence of physical or psychological stimulation, which can be caused by hematologic
disorders, including sickle cell disease and leukemia, spinal cord injuries, and medications.;